The present invention relates to improvements in fluid flow regulators of the type wherein a valving element or flap with two mutually inclined sections is pivotably mounted in a tubular housing or duct and is movable by conveyed fluid (e.g., air, another gas or a liquid) from a fully open position to a partly or fully closed position. Fluid flow regulators of such character are disclosed in my U.S. Pat. Nos. 3,965,928, 3,996,961, and 4,124,037 to which reference may be had, if necessary.
Fluid flow regulators which are disclosed in the above-enumerated patents exhibit many important advantages, especially as concerns the ability of the flap to insure the flow of a conveyed fluid medium at a constant rate even if the pressure of conveyed fluid fluctuates within a wide range. Thus, the flap is sufficiently sensitive to react to changes of the pressure of a fluid medium which is caused to flow through the housing at a relatively low pressure. In most instances, the fluid medium which is conveyed through the housing can readily displace the flap against the opposition of a relatively weak spring which tends to maintain the flap in its fully open position.
The diameter of the housing of a fluid flow regulator to which the present invention pertains cannot be reduced below a certain value for a variety of reasons. At the present time, the minimum inner diameter of a cylindrical housing is approximately 80 mm. This can present problems under certain circumstances, for example, when the fluid flow regulator is installed in or associated with a fan which is used for circulation of air in an office or the like. Thus, it is known that a relatively small fan can be placed onto or close to the desk in an office in order to circulate air for the person using the desk. If the inner diameter of the housing of the fluid flow regulator in such fan is in the range of or exceeds 80 mm, the speed at which air must flow through the housing in order to avoid discomfort to the person using the fan is too low to enable the mass of air to invariably maintain the flap in an optimum position. This holds true even if the flap is biased to the fully open position by a very weak spring.